Method and chemical sensor for determining concentrations of hydrogen peroxide and its precusor in a solution

Abstract

A new electrochemical sensor for determining hydrogen peroxide concentration having a mixed-valence metal oxide of M x O y deposited on an electrode surface thereof is disclosed, wherein M is a transition metal and has two or more than two valences. M x O y , for example, is M 3 O 4 where M is Mn, Fe, Co or Pb, Tb 4 O 7 or Pr 6 O 11 . Further, this invention also discloses an electrochemical sensor for determining a concentration of a hydrogen peroxide precursor, wherein a catalyst is immobilized in the matrix or on the surface of the mixed-valence metal oxide on the electrode. In a typical biochemical system, the catalyst can be a glucose oxidase and blood glucose is catalyzed to form hydrogen peroxide, so that the concentration of blood glucose is determined.

1 . A chemical sensor comprising a transducer which is able to conduct an electric current and a mixed-valence metal oxide deposited on a surface of the transducer, wherein said mixed-valence metal oxide has a formula as follows:  
         M x O y    
       wherein M is a transition metal and has two or more than two different valences; x and y represent moles of said transition metal, M, and oxygen, respectively, provided that 2y=(x 1 )(z 1 )+(x 2 )(z 2 ) . . . +(x n )(z n ), and x 1 +x 2 + . . . +x n =x, wherein z 1 , z 2 , . . . z n  represent the valences of M; x 1 , x 2 , . . . x n  represent moles of M having valences of z 1 , z 2 , . . . z n , respectively, and n is a positive integer.  
     
     
         2 . The chemical sensor according to  claim 1 , wherein M is selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Ga, Nb, Mo, Tc, Ru, Rh, Pd, Ag, In, Sn, W, Re, Ir, Pt, Au, Tl, Pb, Pr and Tb.  
     
     
         3 . The chemical sensor according to  claim 2 , wherein said formula of said mixed-valence metal oxide is M 3 O 4 , and M is Mn and has valences of +2 and +3.  
     
     
         4 . The chemical sensor according to  claim 2 , wherein said formula of said mixed-valence metal oxide is M 3 O 4 , and M is Fe and has valences of +2 and +3.  
     
     
         5 . The chemical sensor according to  claim 2 , wherein said formula of said mixed-valence metal oxide is M 3 O 4 , and M is Co and has valences of +2 and +3.  
     
     
         6 . The chemical sensor according to  claim 2 , wherein said formula of said mixed-valence metal oxide is M 3 O 4 , and M is Pb and has valences of +2 and +3.  
     
     
         7 . The chemical sensor according to  claim 2 , wherein said formula of said mixed-valence metal oxide is M 4 O 7 , and M is Tb and has valences of +3 and +4.  
     
     
         8 . The chemical sensor according to  claim 2 , wherein said formula of said mixed-valence metal oxide is M 6 O 11 , and M is Pr and has valences of +3 and +4.  
     
     
         9 . The chemical sensor according to  claim 1  further comprising a catalyst deposited on the surface of the transducer, wherein said catalyst is able to catalyze a H 2 O 2  precursor to undergo a reaction producing H 2 O 2 .  
     
     
         10 . The chemical sensor according to  claim 9 , wherein said catalyst is glucose oxidase.  
     
     
         11 . The chemical sensor according to  claim 9 , wherein said catalyst is uricase.  
     
     
         12 . The chemical sensor according to  claim 9 , wherein said catalyst is cholesterol oxidase.  
     
     
         13 . The chemical sensor according to  claim 9 , wherein said catalyst is glycerophosphate oxidase.  
     
     
         14 . The chemical sensor according to  claim 9 , wherein said catalyst is sarcosine oxidase.  
     
     
         15 . The chemical sensor according to  claim 9 , wherein said catalyst is polyamine oxidase.  
     
     
         16 . A method for measuring H 2 O 2  concentration in a solution comprising the following steps: 
 a) contacting a counter electrode, a reference electrode and a working electrode with a solution, wherein said working electrode comprises a transducer which is able to conduct an electric current and a mixed-valence metal oxide deposited on a surface of the transducer, wherein said mixed-valence metal oxide has a formula as follows:      M x O y      wherein M is a transition metal and has two or more than two different valences; x and y represent moles of said transition metal, M, and oxygen, respectively, provided that 2y=(x 1 )(z 1 )+(x 2 )(z 2 ) . . . +(x n )(z n ), and x 1 +x 2 + . . . +x n =x, wherein z 1 , z 2 , . . . z n  represent the valences of M; x 1 , x 2 , . . . x n  represent moles of M having valences of z 1 , z 2 , . . . z n , respectively, and n is a positive integer;    b) obtaining an electric current from the working electrode by apmerometry, wherein a fixed potential between the working electrode and the reference electrode is maintained, and said fixed potential ranges from +0.2 V to −0.3V when the reference electrode is 3 M KCl Ag/AgCl electrode; and    c) comparing the electric current from b) with electric currents obtained from solutions having known H 2 O 2  concentrations under substantially the same operating conditions and the same fixed potential used in steps a) and b), so that a concentration of H 2 O 2  in said solution is calculated from said comparison.    
     
     
         17 . The method according to  claim 16 , wherein M is selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Ga, Nb, Mo, Tc, Ru, Rh, Pd, Ag, In, Sn, W, Re, Ir, Pt, Au, Tl, Pb, Pr and Tb.  
     
     
         18 . The method according to  claim 17 , wherein said formula of said mixed-valence metal oxide is M 3 O 4 , and M is Mn and has valences of +2 and +3.  
     
     
         19 . The method according to  claim 17 , wherein said formula of said mixed-valence metal oxide is M 3 O 4 , and M is Fe and has valences of +2 and +3.  
     
     
         20 . The method according to  claim 17 , wherein said formula of said mixed-valence metal oxide is M 3 O 4 , and M is Co and has valences of +2 and +3.  
     
     
         21 . The method according to  claim 17 , wherein said formula of said mixed-valence metal oxide is M 3 O 4 , and M is Pb and has valences of +2 and +3.  
     
     
         22 . The method according to  claim 17 , wherein said formula of said mixed-valence metal oxide is M 4 O 7 , and M is Tb and has valences of +3 and +4.  
     
     
         23 . The method according to  claim 17 , wherein said formula of said mixed-valence metal oxide is M 6 O 11 , and M is Pr and has valences of +3 and +4.  
     
     
         24 . The method according to  claim 16 , wherein step a) further comprises maintaining the solution in a homogeneous phase by stirring, and maintaining a substantially constant pH by adding a pH-buffer, and adding an electrolyte to the solution.  
     
     
         25 . The method according to  claim 24 , wherein said pH-buffer is citrate buffer, glycine buffer, tris-(hydroxymethyl)aminomethane buffer or acetate buffer, and said electrolyte is an alkali metal halide.  
     
     
         26 . The method according to  claim 24 , wherein said formula of said mixed-valence metal oxide is M 3 O 4 , and M is Mn and has valences of +2 and +3, wherein said pH-buffer is glycine buffer, said electrolyte is NaCl, and said fixed potential is −50 mV.  
     
     
         27 . The method according to  claim 24 , wherein said formula of said mixed-valence metal oxide is M 3 O 4 , and M is Fe and has valences of +2 and +3, wherein said pH-buffer is citrate buffer, said electrolyte is NaCl, and said fixed potential is −200 mV.  
     
     
         28 . The method according to  claim 24 , wherein said formula of said mixed-valence metal oxide is M 3 O 4 , and M is Co and has valences of +2 and +3, wherein said pH-buffer is tris-(hydroxymethyl)aminomethane buffer, said electrolyte is NaCl, and said fixed potential is −150 mV.  
     
     
         29 . The method according to  claim 24 , wherein said formula of said mixed-valence metal oxide is M 3 O 4 , and M is Pb and has valences of +2 and +3, wherein said pH-buffer is acetate buffer, said electrolyte is NaCl, and said fixed potential is −200 mV.  
     
     
         30 . The method according to  claim 16 , wherein said electric current is a steady electric current.  
     
     
         31 . The method according to  claim 16 , wherein said electric current is an instant electric current.  
     
     
         32 . A method for measuring a concentration of a hydrogen peroxide precursor in a solution comprising the following steps: 
 a) contacting a counter electrode, a reference electrode and a working electrode with a solution, wherein said working electrode comprises a transducer which is able to conduct an electric current, a catalyst deposited on a surface of the transducer, said catalyst being able to catalyze a H 2 O 2  precursor to undergo a reaction producing H 2 O 2 , and a mixed-valence metal oxide deposited on the surface of the transducer, wherein said mixed-valence metal oxide has a formula as follows:      M x O y      wherein M is a transition metal and has two or more than two different valences; x and y represent moles of said transition metal, M, and oxygen, respectively, provided that 2y=(x 1 )(z 1 )+(x 2 )(z 2 ) . . . +(x n )(z n ), and x 1 +x 2 + . . . +x n =x, wherein z 1 , z 2 , . . . z n  represent the valences of M; x 1 , x 2 , . . . x n  represent moles of M having valences of z 1 , z 2 , . . . z n , respectively, and n is a positive integer;    b) obtaining an electric current from the working electrode by apmerometry, wherein a fixed potential between the working electrode and the reference electrode is maintained, and said fixed potential ranges from +0.2 V to −0.3V when the reference electrode is 3 M KCl Ag/AgCl electrode; and    c) comparing the electric current from b) with electric currents obtained from solutions having known concentrations of said H 2 O 2  precursor under substantially the same operating conditions and the same fixed potential used in steps a) and b), so that a concentration of H 2 O 2  precursor in said solution is calculated from said comparison.    
     
     
         33 . The method according to  claim 32 , wherein M is selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Ga, Nb, Mo, Tc, Ru, Rh, Pd, Ag, In, Sn, W, Re, Ir, Pt, Au, Tl, Pb, Pr and Tb.  
     
     
         34 . The method according to  claim 33 , wherein said formula of said mixed-valence metal oxide is M 3 O 4 , and M is Mn and has valences of +2 and +3.  
     
     
         35 . The method according to  claim 33 , wherein said formula of said mixed-valence metal oxide is M 3 O 4 , and M is Fe and has valences of +2 and +3.  
     
     
         36 . The method according to  claim 33 , wherein said formula of said mixed-valence metal oxide is M 3 O 4 , and M is Co and has valences of +2 and +3.  
     
     
         37 . The method according to  claim 33 , wherein said formula of said mixed-valence metal oxide is M 3 O 4 , and M is Pb and has valences of +2 and +3.  
     
     
         38 . The method according to  claim 33 , wherein said formula of said mixed-valence metal oxide is M 4 O 7 , and M is Tb and has valences of +3 and +4.  
     
     
         39 . The method according to  claim 33 , wherein said formula of said mixed-valence metal oxide is M 6 O 11 , and M is Pr and has valences of +3 and +4.  
     
     
         40 . The method according to  claim 32 , wherein step a) further comprises maintaining the solution in a homogeneous phase by stirring, and maintaining a substantially constant pH by adding a pH-buffer, and adding an electrolyte to the solution.  
     
     
         41 . The method according to  claim 40 , wherein said pH-buffer is citrate buffer, glycine buffer, tris-(hydroxymethyl)aminomethane buffer or acetate buffer, and said electrolyte is an alkali metal halide.  
     
     
         42 . The method according to  claim 40 , wherein said formula of said mixed-valence metal oxide is M 3 O 4 , and M is Mn and has valences of +2 and +3, wherein said pH-buffer is glycine buffer, said electrolyte is NaCl, and said fixed potential is −50 mV.  
     
     
         43 . The method according to  claim 40 , wherein said formula of said mixed-valence metal oxide is M 3 O 4 , and M is Fe and has valences of +2 and +3, wherein said pH-buffer is citrate buffer, said electrolyte is NaCl, and said fixed potential is −200 mV.  
     
     
         44 . The method according to  claim 40 , wherein said formula of said mixed-valence metal oxide is M 3 O 4 , and M is Co and has valences of +2 and +3, wherein said pH-buffer is tris-(hydroxymethyl)aminomethane buffer, said electrolyte is NaCl, and said fixed potential is −150 mV.  
     
     
         45 . The method according to  claim 40 , wherein said formula of said mixed-valence metal oxide is M 3 O 4 , and M is Pb and has valences of +2 and +3, wherein said pH-buffer is acetate buffer, said electrolyte is NaCl, and said fixed potential is −200 mV.  
     
     
         46 . The method according to  claim 32 , wherein said catalyst is glucose oxidase, and said H 2 O 2  precursor is glucose.  
     
     
         47 . The method according to  claim 32 , wherein said catalyst is uricase, and said H 2 O 2  precursor is urea.  
     
     
         48 . The method according to  claim 32 , wherein said catalyst is cholesterol oxidase, and said H 2 O 2  precursor is cholesterol.  
     
     
         49 . The method according to  claim 32 , wherein said catalyst is glycerophosphate oxidase, and said H 2 O 2  precursor is triglyceride.  
     
     
         50 . The method according to  claim 32 , wherein said catalyst is sarcosine oxidase, and said H 2 O 2  precursor is creatinine.  
     
     
         51 . The method according to  claim 32 , wherein said catalyst is polyamine oxidase, and said H 2 O 2  precursor is polyamine.  
     
     
         52 . The method according to  claim 32 , wherein said electric current is a steady electric current.  
     
     
         53 . The method according to  claim 32 , wherein said electric current is an instant electric current.